Food products which are distributed to normal retail outlets generally fall into the following categories:
Category 1--Those refrigerated food products which are perishable and normally frozen, e.g., prepared frozen food products, ice creams, frozen juice concentrates, some meats, etc. PA0 Category 2--Those refrigerated food products which are perishable and normally maintained above but nevertheless near freezing temperatures (usually in the 32.degree.-45.degree. F. range), e.g., whole and pasteurized milks, butter, some prepared meats, etc. PA0 Category 3--Those refrigerated food products which are perishable and normally maintained at sub-ambient temperatures (usually in the 45.degree.-55.degree. F. range), sometimes to suppress dehydration, e.g., fresh produce, such as lettuce, cabbage, celery, etc., some prepared meats, dairy products, some canned goods, etc. PA0 Category 4--Those food products which need not be refrigerated and can normally tolerate ambient temperature conditions for at least short periods of time, e.g., many canned goods, soft drinks, most bakery products, etc.
There is no problem distributing such food products to large retail outlets that are capable of receiving and handling truck load quantities. In such cases, a suitable transportation vehicle is selected for the food product category to be transported to the retail outlet. Those food products which are frozen or refrigerated are normally transported on vehicles that are suitably equipped with an insulated van body and an appropriate refrigeration unit. Those food products which can tolerate ambient temperatures, however, are usually transported in uninsulated and nonrefrigerated transportation equipment.
The distribution of such food products to small retail outlets which handle all four food product categories but which are unable to economically receive and handle the large truck load quantities, creates a distribution problem for the large distributor and which ultimately leads to higher costs to the small retailer. For one, it is more or less impossible to transport all four categories of food products in the same van body since the temperature requirements for each category is different. In practice, this is partially overcome by various procedures. In many cases, insulated and mobile food lockers are used for housing the frozen food products in the van body. In such cases, the low temperatures are maintained through the use of dry ice (solid carbon dioxide) in the lockers. Fresh produce, on the other hand, is usually iced down in their shipping cartons with conventional ice (frozen water) and many of the remaining food products in the refrigerated categories are simply omitted from the shipments and left for purchase by the small retailer at the higher prices often charged by local suppliers.
The above practices have many disadvantages. They almost make it mandatory that a vehicle with an expensively insulated van body be used even though some of the food products being transported do not require refrigeration. Furthermore, the mixing of iced down produce and boxed food products in the same compartment often leads to water absorption by the cardboard containers for reasons of inadequate drainage of the water derived from the melting ice. Furthermore, the mixing of the various food product categories in the van body lends to inefficient use of the interior space if easy access to each category is to be realized through use of the conventional van body structures currently being used in the distribution of such food products to the retailers.
As will be seen, the invention relates to a food product transport system which involves a land vehicle with a van body, an insulated and mobile cargo carrier for containing the food products that require sub-ambient temperature conditions, and which, during transportation of the food products, is securely located in the van body. The system also contemplates a refrigeration unit that is mounted on the land vehicle and used in maintaining the sub-ambient temperature conditions within the mobile cargo carrier.
Insulated cargo carriers for use in transporting perishable food products under controlled temperature conditions from one location to another on over land and/or over sea vehicles are known. They range in size from relatively small food lockers which are equipped with wheels that facilitate their movement about a work area without the need for auxiliary lifting equipment to relatively large cargo containers that require auxiliary lifting equipment for their translocation in and about a work area.
The desire in using such carriers is to control the temperature in the food product carrier at a sub-ambient temperature such as to avoid spoilage of the contained food product during transit. As such, various different methods of conditioning the air in the carriers during transportation have evolved.
To attain and maintain sub-ambient temperatures, the carrier is equipped, in some cases, with an electrically powered refrigeration system which connects with the electrical power supply of the vehicle. (See Cantagalloet et al., U.S. Pat. Nos. 3,699,870 and 3,733,849.) Such systems take up valuable space in the structure forming the carrier and dissipate the heat extracted from within the container to the atmosphere externally thereof. This precludes the transporation of such containers within a closed van body structure of an over land vehicle because the heat, thus dissipated, accumulates within the van body and causes extreme temperature rises which result in refrigeration equipment overloads and damages. As such, large carriers which are thus equipped with their own refrigeration systems are mainly transported on so-called "flat bed" types of land vehicles.
To arrive at or maintain the sub-ambient temperature conditions in the cargo carriers in other cases, the carriers have been equipped with internal evaporator coils in which a refrigerant that is supplied from an external source is evaporated to extract the internal heat. (See Tetrick et al., U.S. Pat. Nos. 3,507,322 and 3,468,369; and McSheehy et al., U.S. Pat. No. 3,898,854.) Although such carriers are mainly adapted for connection with the refrigerant supplying components of a refrigeration system at fixed land locations, it has been advocated to equip vehicles with the necessary refrigeration supply components. In such cases, the evaporator coils of the carriers are connected to the refrigerant supply components on the vehicle at the time the carriers are loaded and are thereafter disconnected from the system at the time of unloading. The main problem with this type carrier arrangements is that it requires the mounting on the vehicle of a partial refrigeration system which is only useful when the evaporator coil equipped cargo carriers are being transported thereby. This type of system is primarily limited to use with small lockers or containers because the large confined areas involved in large carriers require the use of fans in attaining satisfactory movement of air with respect to the evaporation coils.
Another type of perishable food carrier is that which relies on the insertion of a cryogenic fluid such as liquid nitrogen into the carrier and wherein it is evaporated to extract the heat. (See Hill et al., U.S. Pat. No. 3,557,569.) Such carriers are merely adapted to receive the cryogenic material internally from an external source which may be provided in the form of a suitable tank of the cryogenic material that is conveniently mounted on the individual container per se or on the vehicle.
Still another type of perishable food carrier is that which is adapted for coupling with the inlet and outlet of the fan used for circulating the air over the evaporation coils of a refrigeration system. (See Westling et al., U.S. Pat. No. 3,359,752.) This type of container has the advantage that conventional refrigeration systems in commercial use on over land vehicles may be used for controlling the temperature in the containers at the desired sub-ambient levels.